Vulnerability details
CVE-2026-63209
klauspost compress
Integer Overflow or Wraparound and Out-of-bounds Write in compress
CVSS 3.1
7.5High
Official description
compress provides various compression algorithms. Prior to version 1.18.7, a signed integer overflow vulnerability in s2.NewDict() allows an attacker to bypass repeat index validation by supplying a dictionary with a uvarint-encoded repeat value exceeding MaxInt64. When Dict.Encode() is subsequently called, the overflowed negative repeat value causes an out-of-bounds memory access via unsafe.Pointer arithmetic, crashing the process with SIGSEGV. This issue has been patched in version 1.18.7.
CVSS scores
| Score | Version | Source | Vector |
|---|---|---|---|
| 7.5High | 3.1 | CVEProject cvelistV5 (CNA) (GitHub_M) | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Affected products
| Vendor | Product | Versions | Source |
|---|---|---|---|
| klauspost | compress | < 1.18.7 | CVEProject cvelistV5 (CNA) |
References and advisories
3- https://github.com/klauspost/compress/commit/539243b8823ee8f03e49969823d57c348c917536 x_refsource_MISC
- https://github.com/klauspost/compress/releases/tag/v1.18.7 x_refsource_MISC
- https://github.com/klauspost/compress/security/advisories/GHSA-259r-337f-4rfw x_refsource_CONFIRM
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Details
- Published
- 2026-09-29
- Last updated
- 2026-09-29
- State
- Published
- Assigner (CNA)
- GitHub_M
Exploit prediction (EPSS)
0.57%
Probability of exploitation in 30 days
47.4%
Percentile (among all CVEs)
SSVC assessment (CISA)
- Automatable
- Yes
- Exploitation
- None
- Technical impact
- Partial
Weaknesses (CWE)
- CWE-190Integer Overflow or Wraparound
- CWE-787Out-of-bounds Write